The present invention relates to novel norbornene polymers, and a production process thereof. The norbornene polymers according to the present invention are excellent in heat resistance and can provide molded or formed products extremely small in distortion at high temperature. The present invention also relates to molding materials comprising such a norbornene polymer and molded or formed products making use of such a molding material.
Thermoplastic norbornene polymers such as tetracyclododecene ring-opening polymers and hydrogenated products thereof are excellent in optical properties such as transparency and low birefringence, weathering properties such as moisture resistance and heat resistance, and electrical properties such as low dielectric constant and low dielectric loss tangent and are hence used as molding materials in various application fields making good use of these properties.
For example, in Japanese Patent Application Laid-Open Nos. 276253/1992, 276537/1992 and 317411/1993, and U.S. Pat. No. 5,468,803, it is reported that thermoplastic norbornene resins are excellent in gas barrier property, low in moisture permeability and little in substances dissolved out and are hence suitable for medical equipments.
In Japanese Patent Application Laid-Open Nos. 138257/1989, 63807/1992 and 41550/1995, it is reported that thermoplastic norbornene resins are excellent in electrical properties such as dielectric constant and dielectric loss tangent, and low in dependence of these electrical properties on temperature and frequency, and are hence suitable for use as electrical insulating materials. In particular, it is reported in Japanese Patent Application Laid-Open No. 63807/1992 that when a thermoplastic norbornene resin is used as a capacitor film, a miniaturized capacitor having high capacitance is provided.
International Publication WO96/10596 discloses that of such thermoplastic norbornene resins, hydrogenated products of norbornene ring-opening polymers obtained by subjecting a norbornene monomer having an aromatic ring in its fused polycyclic structure, such as 1,4-methano-1,4,4a,9a-tetrahydrofluorene (MTF), to ring-opening polymerization and then hydrogenating the resultant ring-opening polymer to saturate the double bond in the main chain and convert the aromatic rings into cyclohexane rings are low in birefringence and excellent in resistance to deterioration by oils and greases compared with the conventional thermoplastic norbornene resins and are hence useful in such various uses as described above, including optical materials. Japanese Patent Application Laid-Open No. 220230/1991 discloses that hydrogenated products of norbornene ring-opening polymers obtained by subjecting a norbornene monomer having a cyclohexene ring in its fused polycyclic structure, such as 1,4-methano-1,4,4a,4b,5,8,8a,9a-octahydro-9H-fluorene (MOF), to ring-opening polymerization and then hydrogenating the resultant ring-opening polymer to saturate the double bond in the main chain and convert the cyclohexene rings into cyclohexane rings are also transparency and low birefringence and are hence suitable for use as optical materials.
As described above, the norbornene polymers having a cyclohexane ring in its fused polycyclic structure constituting a repeating unit are resin materials having characteristics such as low birefringence and excellent transparency and resistance to deterioration by oils and greases. However, the conventionally known norbornene polymers have a glass transition temperature (Tg) of at most about 140xc2x0 C., and so their heat resistance has not been insufficient. When another copolymerizable monomer is copolymerized with a norbornene monomer, for example, upon production of a ring-opening polymer in order to improve the processability and strength properties of the resulting norbornene polymer, there has been a problem that Tg of the hydrogenated product of the ring-opening copolymer finally obtained is lower than Tg of the hydrogenated product of the homopolymer of such a norbornene monomer. Accordingly, the norbornene polymers having a cyclohexane ring in its fused polycyclic structure constituting a repeating unit have been difficult to meet strict requirements of heat resistance in recent years.
It is an object of the present invention to provide a norbornene polymer excellent in heat resistance and extremely small in distortion at high temperature, and a production process thereof.
Another object of the present invention is to provide a molding material comprising such a norbornene polymer and a molded or formed product formed of such a molding material.
The present inventors have carried out an extensive investigation with a view toward obtaining norbornene polymers having greatly improved heat resistance while retaining properties such as excellent transparency, low birefringence and resistance to oils and greases inherent in the norbornene polymers having a cyclohexane ring in its fused polycyclic structure constituting a repeating unit. As a result, it has been found that the compositional ratio of stereoisomerism (endo-exo isomerism) of a norbornene monomer having a fused polycyclic structure containing a norbornene ring is controlled to conduct ring-opening polymerization or addition polymerization using a norbornene monomer containing at least 50 mol % of endo form, and hydrogenation is then performed under comparatively moderate temperature conditions, thereby obtaining a norbornene polymer having excellent heat resistance without impairing other properties.
The norbornene polymers according to the present invention can be identified by performing 13C-NMR spectrum analysis to determine areas of both methylene peaks on high magnetic field and low magnetic field sides, which are derived from the methylene groups in cycloalkane (for example, cyclohexane ring) formed by hydrogenating an aromatic ring or cycloalkene in the fused polycyclic structure, and calculating out a peak area ratio thereof. The norbornene polymers according to the present invention may be those derived from copolymers of the above-described norbornene monomer and another monomer copolymerizable therewith.
The norbornene polymers according to the present invention may be used as molding materials by compounding fillers, stabilizers, other thermoplastic resins, rubbery polymers and/or the like as needed. The molding materials according to the present invention can be formed into various kinds of molded or formed products such as medical equipments, optical members, electrical insulating members and electronic part treating equipments.
The present invention has been led to completion on the basis of these findings.
According to the present invention, there is thus provided a norbornene polymer comprising a repeating unit derived from a norbornene monomer having a cyclic hydrocarbon structure (I) derived from the norbornene ring which constitutes at least a part of the main chain, another cyclic hydrocarbon structure (II), which shares one carbon-carbon bond with the cyclic hydrocarbon structure (I) and has 4 to 6 carbon atoms, and a monocyclic or polycyclic hydrocarbon structure (III), which shares one carbon-carbon bond with the cyclic hydrocarbon structure (II), in a proportion of 20 to 100 mol % based on the whole repeating unit of the polymer, wherein the number average molecular weight is within a range of 1,000 to 1,000,000, and a peak area (A) on a high magnetic field side and a peak area (B) on a low magnetic field side in methylene peaks derived from the methylene groups in the cyclic hydrocarbon structure (III) in a 13C-NMR spectrum as determined in heavy chloroform (TMS standard) satisfy a relationship of the expression:
B/(A+B)xe2x89xa60.30
According to the present invention, there is also provided a process for producing the above-described norbornene polymer, which comprises polymerizing a monomer or monomer mixture comprising 20 to 100 mol % of a norbornene monomer (1) of a fused polycyclic structure having a norbornene ring structure (IA), a cyclic hydrocarbon structure (IIA), which shares one carbon-carbon bond with the norbornene ring structure (IA) and has 4 to 6 carbon atoms, and a monocyclic or polycyclic hydrocarbon structure (IIIA), which shares one carbon-carbon bond with the cyclic hydrocarbon structure (IIA) and has at least one carbon-carbon unsaturated bond in its ring, the compositional ratio (a:b) between an endo form (a) and an exo form (b) which are stereoisomers of said norbornene monomer being within a range of 70:30 to 100:0, and 0 to 80 mol % of any other monomer (ii) copolymerizable with the norbornene monomer, and then hydrogenating the resultant polymer.
According to the present invention, there are further provided a molding material comprising the above-described norbornene polymer, and a molded or formed product formed of the molding material.